ES2561602T3 - Synchronous rectifier - Google Patents

Abstract

Synchronous rectifier (16) for integration into a current source (10) to facilitate a direct current, in particular in a cube-shaped or parallelepiped-shaped unit of a high-amperage transformer (12) with elements (24) of switching, an excitation circuit (17) for exciting the switching elements (24) and a supply circuit (48), a printed circuit board (35) being provided with tracks and connecting surfaces for housing electronic components , the switching elements (24) being arranged, the excitation circuit (17) and the supply circuit (48) for the autarkic operation on the printed circuit board (35), characterized in that on the circuit board (35) printed are provided several openings (37) arranged in parallel and in series to accommodate convexities (36) of a contact plate (29), openings (37) through which they are arranged and joined, or else Tin-plated switching elements (24), switching elements (24) that can be spliced with the convexities (36) of the contact plate (29).

Description

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DESCRIPTION

Synchronous rectifier

The invention relates to a synchronous rectifier for integration into a current source to facilitate a direct current, in particular in a cube or parallelepiped unit of a high amperage transformer, with switching elements, an excitation circuit. to excite the switching elements and a supply circuit, a printed circuit board with tracks and connection surfaces for housing electronic components being provided.

The present invention relates mainly, but not exclusively, to synchronous rectifiers for current sources with resistance welding devices, in particular, spot welding devices, in which particularly high continuous currents appear in the magnitude of some kA. Also covered by the object of the present patent application are synchronous rectifiers for current sources for other devices, in which high continuous currents of this type are used. Examples for such devices are battery charging devices, particle accelerators, galvanizing mechanisms or the like. WO 2007/041729 A1 describes, for example, a battery charging apparatus and a current transformer for the production of a duly high direct current.

In resistance welding devices, the necessary high continuous currents are provided, with the help of high-amperage transformers and corresponding rectifiers. Due to the high currents that appear, the diode rectifiers are disadvantageous due to the relatively high losses, which is why mainly active rectifiers with switching elements that are formed by corresponding transistors are used. But also resistance welding devices with active rectifiers, for example synchronous rectifiers, have relatively high losses, and therefore relatively low yields. Since in the state of the art, due to the separate conventional construction, for example of transformer of great amperage and rectification, considerable lengths of lines and therefore loss of lines occur, very bad performance due to high currents is caused .

For example, document DE 10 2007 042 771 B3 describes a procedure for the operation of the current supply of a resistance welding device using a synchronous rectifier by means of which the lost power can be reduced and the performance improved.

In manufacturing trains in the automobile industry a plurality of spot welding devices (often about 100 to 1000 individual devices) are used for the manufacture of different joints in the body and in the chassis of the vehicle to be manufactured. After causing single point welding devices to cause very high losses due to high amperage transformers and switching lines and elements, in such manufacturing trains, the total losses that appear move in enormously high dimensions, for example between 1 MW and 50 MW. Since the losses are mainly reflected in the form of lost heat, measures must be taken in turn to expel the heat, so that the entire energy balance becomes even worse. WO 2004/044959 shows a synchronous rectifier according to the preamble of claim 1. EP 2043412 shows a printed circuit board with openings arranged in series to accommodate convexities of a contact plate, openings through which The switching elements, switching elements that can contact the convexities of the contact plate, are arranged and welded with tin.

An additional advantage is produced because the high losses for installations of this type require very high connection network power, which results in very high costs for the manufacture, commissioning and operation of an installation. this type.

For the production of a single welding point with a welding current of 20 kA, according to the state of the art from the current perspective, for example a connection power of the supply network of up to 150 kW is required, resulting in the In the case of the welding current mentioned losses of up to 135 WV, so a very bad performance of only about 10% is achieved.

The objective of the present invention is therefore the creation of a synchronous rectifier for Integration into a current source to facilitate a direct current, through which losses can be reduced and energy balance and performance can be improved. . The disadvantages of known devices should be reduced or avoided.

This objective is achieved because the switching elements, the excitation circuit and the supply circuit for self-loading operation are arranged on the printed circuit board, several openings arranged in parallel and in series to accommodate on the printed circuit board are provided. convexities of a contact plate, openings through which the switching elements are arranged and connected, or tin-welded, switching elements that can be contacted with the convexities of the contact plate. In this regard it is advantageous, that in the assembly of the printed circuit board of the synchronous rectifier on a contact plate, the contact plate connections protrude through the openings in the Printed circuit board, so that at the same time the back side of the printed circuit board can be attached either

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welded with tin in a safe manner with the contact plate, and can also be attached or soldered with the contact plate with switching elements arranged on the opposite side. Therefore the high cost of wiring can be suppressed. A simple post-cloning of the Printed circuit board is also possible on the contact plate and it can no longer slide during tin welding.

Because the switching elements are arranged on the printed circuit board, the excitation circuit and the supply circuit of the synchronous rectifier can achieve an autarkic construction. For example, the printed circuit board can be integrated into the high amperage transformer. If the synchronous rectifier is configured for automatic operation in the high amperage transformer, all lines to the printed circuit board can be avoided and therefore in the high amperage transformer. If all components for the operation of the high amperage transformer, such as the switching elements, the excitation circuit and the supply circuit are integrated on the printed circuit board, only one piece of power must be connected to the input side, and on the output side the respective consumer.

By means of the switching elements of the synchronous rectifier arranged on the printed circuit board, the synchronous rectifier can therefore be connected without lines to the output of the high amperage transformer, so losses can be significantly reduced.

Additionally, it is advantageous if the excitation circuit is arranged on both sides of the switching elements arranged in parallel and in series on the printed circuit board, since this shortens the line paths to the individual switching elements. . Therefore it can be ensured that all switching elements switched in parallel are connected within a very short period of time. By means of the arrangement on both sides of the excitation circuit, a reduction of half the line length is achieved and therefore accompanied by a reduction of the line inductances and therefore an essential shortening of the switching times.

If the excitation circuit is connected with at least one sensor, in particular a current transformer, integrated in the high amperage transformer, an exact control or regulation is possible, since by means of the at least one sensor the states can be registered in The high amperage transformer.

Advantageously, the supply circuit is configured for the formation of duly high switching currents, for example between 800 A and 1500 A, in particular 1000 A and for the supply of the components with corresponding supply voltage. Due to the very high switching current, a very short switching time can be achieved, in particular in the range of ns. With this, it can be guaranteed that the switching elements are always switched to zero or directly shortly before the zero crossing with little output current, so that they hardly appear, or no switching loss appears.

If a data communication circuit is provided for wireless, preferably inductive, magnetic or Bluetooth data transmission, it is advantageously achieved that data can be transmitted wirelessly from or to the printed circuit board of the synchronous rectifier. For this, an adaptation of the switching moments can be made to different fields of use of the high amperage transformer. Likewise, from a memory provided on the printed circuit board of the synchronous rectifier, data can be read for further processing or control or for quality supervision.

Finally, an advantageous configuration is provided in which on one side of the printed circuit board, a surface that can be joined by indirect welding to weld with tin with the contact plate is provided on the entire surface, since this can be achieved a secure connection with the contact plate. Therefore, the step resistors can also be substantially reduced, since a link across the entire surface of the printed circuit board has a lower step resistance.

The invention is explained in more detail by the attached drawings.

They show:

figure 1

figure 2

figure 3

Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

a state-of-the-art resistance welding device with a robot and electrode holder clamps attached thereto in schematic representation;

a schematic block diagram of a resistance welding device with a current source to facilitate the welding current;

a resistance welding device, in particular an electrode holder clamp, with an integrated current source to facilitate the welding current in schematic representation; a schematic block diagram of the current source to facilitate welding current; an embodiment of the current source to facilitate a direct current; the current source according to figure 5 in exploded view; the current source according to figure 5 with marked course of the cooling channels; a view of the high amperage transformer on the I support of the current source; the support in I according to figure 8 in sectioned representation;

a contact plate of the high-amperage transformer of the current source together with the printed circuit board of the synchronous rectifier and the excitation circuit;

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figure 11 figure 12

figure 13

figure 14

figure 15

figure 16

the contact plate according to figure 10 in sectioned representation;

a secondary winding of the high amperage transformer with current transformer in

exploded representation;

the construction of a secondary winding of the high amperage transformer in exploded representation;

a block diagram of a circuit for the supply of the synchronous rectifier and the excitation circuit with electric power;

a time course of the supply voltage of the supply circuit according to figure 14; Y

Time traces to illustrate the excitation of the switching elements of a synchronous rectifier as a function of the secondary currents of the high amperage transformer.

In the illustrated embodiment shown in FIG. 1 to 16, a construction of a resistance welding device 1 with the essential components is described. For the same pieces the same reference numbers were given in the figures.

Figure 1 shows in perspective a resistance welding device 1 for resistance welding of at least two work pieces 2, 3 with a robot for handling. The resistance welding device 1 is composed of an electrode holder clamp 4 fixed on the robot with two arms 5 of clamps on which housings 6 are arranged to accommodate in each case an electrode 7. Around each electrode 7 runs in each case a tape 8 that reduces the resistance of resistance welding resistance, and protects the electrodes 7. In addition, the reproduction originated in the band 8 of the manufactured welding point can be analyzed and consulted to assess the welding quality. The tape 8 to protect the electrodes 7 is unwound from a winding device 9 that can be arranged on the electrode holder 4 or the clamp arms 5, and is conducted along the clamp arms 5, of the housings 6 of electrodes and electrodes 7 back to the winding device 9, where the tape 8 is wound again. For the realization of spot welding, the welding current that is supplied from a corresponding piece of power 19 is conducted through the electrodes 7. Thus, the work pieces 2, 3 are joined together by a point of welding that originates in the spot welding operation. Typically, the power part 19 is, to facilitate the welding current, outside the resistance welding device 1, as schematically shown in Figure 1. The welding current is guided through lines 11 corresponding to the electrodes 7 or the clamp arms 5 electrically configured. Due to the amplitude of the welding current in the range of some kA, duly large cross sections are necessary for the lines 11, whereby resulting in high ohmic losses.

In addition, long primary supply lines lead to a high inductance of lines 11, whereby the switching frequency with which a high-amperage transformer 12 of a current source 10 is limited is limited, resulting in transformers 12 Great amperage very large. In the state of the art, the power part 19 is in a distribution cabinet next to the welding robot, so that very long supply lines are necessary, for example up to 30 m to the large amperage transformer 12 for the electrode holder 4 on the robot.

With the solution according to the invention a reduction in weight and considerable size is achieved, so that a positioning of the power piece 19 is directly possible on the robot, in particular in the area of the clamp housing. Additionally, the power piece 19 is preferably made chilled in water.

Figure 2 shows a schematic block diagram of a resistance welding device 1 with a current source 10 to facilitate the welding current. Although in the embodiment shown the current source 10 serves to facilitate the welding current for the resistance welding device 1, the current source 10 can be consulted, in particular the entire structure of the current supply also to facilitate a current Continue for other applications. The current source 10 contains a high amperage transformer 12 with at least one primary winding 13, at least one secondary winding 14 with central branch and a magnetic core 15. The current transformed with the aid of the high amperage transformer 12 is rectified in a synchronous rectifier 16 and is fed to the clamp arms 5 or electrodes 7 of the resistance welding device 1. For the control of the synchronous rectifier 16, an excitation circuit 17 is provided. The excitation circuit 17 sends control pulses corresponding to the switching elements 24 of the synchronous rectifier 16 due to the secondary currents of the high amperage transformer 12 measured for example by means of current transformers 18.

As is generally known, due to the high welding currents by adding the necessary line length both considerable ohmic and / or inductive losses appear, as well as passage and switching losses in the switching elements 24 of the synchronous rectifier 16. In addition, losses also occur in the rectifier, in the supply for the synchronous rectifier 16 and the excitation circuit 17. The resulting performance of resistance welding devices 1 of this type is correspondingly low.

To generate the primary current of the high amperage transformer 12, a power part 19 is provided that

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It is arranged between a supply network and the current source 10. The power part 19 facilitates the primary current for the high amperage transformer 12 or the current source 10 with the desired amplitude and the desired frequency.

Figure 3 shows a resistance welding device 1 with current source 10 integrated in schematic representation. In this case, the current source 10 directly, in particular as a support element, is arranged on the electrode holder clamp 4 or the clamp arms 5 of the resistance welding device 1, so that at least a part of the lines 11 for guiding the welding current towards the electrodes 7 it can be omitted, and therefore the line lengths can be shortened essentially, since only the connection with a clamp arm 5 is necessary. The current source 10 presents at least four contacts 20, 21, 22, 23 for forming a multi-point splice, two first contacts 20, 21 of one polarity being connected with one of the clamp arms 5 and two additional contacts 22, 23 of an opposite polarity with the other arm 5 of the clamp. Advantageously, the first two contacts 20, 21 are arranged in each case facing one of the polarities, and the other two contacts 22, 23 with the other polarity, the other two contacts 22, 23 being arranged essentially 90 ° arranged with respect to others in front of the first two contacts 20, 21. By splicing multiple points, lines that are usually necessary to join the secondary side 14 of the high amperage transformer 12 with the clamp arms 5 or the electrodes 6 of the junction can be avoided. resistance welding device 1, or its length reduced and therefore the ohmic losses as well as contact losses can be significantly reduced. Therefore, lines as short as possible can be used with cross-sections as large as possible, while remaining flexible with the electrode holder 4. An additional advantage is that, due to such a splice, losses are reduced, in particular contact step resistors. Due to the at least four contacts 20, 21, 22, 23, the welding current to be transmitted can be reduced by half, so that a reduction in step losses is also caused, given that through the essential increase in active contact surfaces reduce the resistance of passage. For example, each of the four contacts 20, 21, 22, 23 in the dimensioning of a high amperage transformer 12, or of a current source 10, to facilitate a continuous current of 20 kA has a surface between 15 cm x 15 cm up to 25 cm x 25 cm, preferably 20 cm x 20 cm.

In the exemplary embodiment shown, the current source 10 is configured substantially in the form of a hub, the lateral surface of the hub forming the contacts 20, 21, 22, 23. The first two contacts 20, 21 are connected to one of the electrodes 7 and the other two contacts 22, 23 are connected to the other electrode 7 of the resistance welding device 1 by the clamp arms 5. As can be seen from the partial exploded view, at least one caliper arm 5, in particular the lower caliper arm 5, is joined by a support element 23a of the lower caliper arm 5, while the other, in particular the upper clamp arm 5 is connected by a flexible connection clamp 23b with the other contacts 22, 23. At least one clamp arm 5 is therefore directly connected with the high amperage transformer 12 and the other clamp arm 5 by a very short line, for example shorter than 50 m, is connected to it. Because the lines 11 between the current source 10 and the electrodes 7 or the clamp arms 5 of the resistance welding device 1 are omitted or too short, the ohmic losses and inductive losses are clearly reduced.

Special advantages are produced when at least two contacts 20, 21 are connected directly or without lines and therefore without contact passage resistors with an arm 5 of tweezers. This can be achieved by the fact that in the current source 10 these two contacts 20, 21 are almost integrated, which are connected to the corresponding parts of the resistance welding device 1, in particular the clamp arms 5, that is to say without laying lines. By means of the direct connection of a clamp arm 5 with the contacts 20, 21 of the high amperage transformer 12, a connection without lines is therefore achieved, while the second clamp arm 5 must be connected with very short lines with the contacts 22, 23. With this, a very high reduction in line losses can be achieved, since the line lengths are reduced to a minimum. In the state of the art, in the optimum case, the high amperage transformer is positioned as close as possible to the electrode holder 4, so that the lines must then be routed from the high amperage transformer 12 to the electrode holder 4 , while in the solution according to the invention the high amperage transformer 12 is integrated in the electrode holder clamp 4 and at the same time an arm 5 clamps is fixed directly on the high amperage transformer 12, so that only the second arm 5 of clamp with one or two short lines. Of course, instead of lines, for example, sliding contacts or other connecting elements can also be used. Also the losses within the current source 10, due to the compact construction mode, and the direct connection, that is to say without lines, of the components of the current source 10 are markedly reduced.

Advantageously, all the components of the current source 10, as well as the synchronous rectifier 16, the excitation circuit 17, the current transformer 18, and all the supply circuits for the synchronous rectifier 16 and the circuit 17 excitation are contained in the unit in the form of a cube or parallelepiped. That is, by integrating the electronic components / circuits a construction unit is created in the form of a cube, in which the user must provide only energy in the primary side in the form of corresponding alternating voltage, or corresponding alternating current to obtain on the secondary side a correspondingly sized direct current, or a correspondingly sized continuous voltage with high power. The control and regulation is carried out automatically in the

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cube or current source 10. With this, the hub or the current source 10 can be used extensively for the supply of components with high direct current. In particular, the current source 10 serves for supply with reduced voltage and high amperage, as is usual in resistance welding processes.

In use in a resistance welding process, parts of the current source 10 configured in the form of a cube can also be formed by components of the resistance welding device 1, for example parts of the arms 5 of pliers or the like, such as this It is represented. In this case, the cube or the current source 10 assumes a support function, as a pin arm 5 is fixed directly on the cube. The additional clamp arm 5 is spliced by joining lines (not shown). Through this construction, long feed lines can be prevented, so that a substantial reduction in losses is achieved. However, in order for the hub to be integrated into an electrode holder 4 of this type, it is necessary that its construction size be kept as small as possible. For example, the cube or the current source 10, in a dimensioning of the direct current to be provided up to 20 kA, has a lateral length between 10 cm and 20 cm, in particular 15 cm. By means of this compact configuration of the cube-shaped current source 10 it is simply possible to integrate this, for example, into the base body of the electrode holder 4.

Figure 4 shows a schematic block diagram of the current source 10 to facilitate a direct current, in particular of a welding current. In this preferred embodiment variant of the current source 10, ten primary windings 13 of the high amperage transformer 12 and ten secondary windings 14 of the large amperage transformer 12 are switched in parallel with central bypass. By such an embodiment of the high amperage transformer 12, the correspondingly high transmission ratio to achieve a correspondingly high secondary current can also be achieved in the case of reduced turns of primary windings 13 and reduced turns of windings. Secondary 14. For example, with ten primary windings 13 and also ten secondary windings 14, a transmission ratio of 100 can be achieved. The primary current crosses the primary windings 13 in series switching of the high amperage transformer 12, while the secondary current relatively High is distributed in the ten secondary windings 14 switched in parallel. The partial currents on the secondary side are fed to the corresponding switching elements 24 of the synchronous rectifier 16. A distribution of this type occurs, despite the reduced turns on the primary and secondary sides, a correspondingly high transmission ratio. (in this case 100). By means of this construction, unlike the usual large amperage transformers, smaller numbers of turns are necessary on the primary side, whereby the length of the primary winding 13 can be reduced, and therefore the ohmic losses can be reduced. By means of the reduced number of turns of the primary winding 13 and therefore a resulting reduction in the line length, the dispersion inductance of the high-amperage transformer 12 typical of the system is again reduced, whereby the high-amperage transformer 12 It can operate with higher switching frequencies, for example 10 kHz. The higher switching frequencies with respect to conventional high-amperage transformers once again cause a decrease in the construction size and the weight of the high-amperage transformer 12, and therefore of the advantageous mounting possibilities. Therefore, the high amperage transformer 12 can be positioned, for example, very close to the electrodes 7 of a resistance welding device 1. Therefore, the support load of the welding robot can also be reduced due to the reduced weight of the high amperage transformer 12, so that a cheaper small welding robot may be sufficient.

Conventional transformers, in which no series / parallel switching of the primary and secondary winding is performed, would correspondingly require more primary turns, which would result in substantially longer cable lengths on the primary side. Due to the longer cable length, ohmic losses increase on the one hand, and on the other hand it results in a higher dispersion inductance, so the frequencies with which the state of the art transformer can operate are limited in some kHz

In contrast to this, in the construction of the high amperage transformer 12 described in this case, the ohmic losses and the dispersion inductance of the primary windings 13 and secondary windings 14 conditioned by the system are reduced, so frequencies can be used in the range of 10 kHz and higher. Therefore, a substantially smaller construction size of the high amperage transformer 12 can be achieved. The smallest construction size of the high amperage transformer 12 or of the current source 10 'makes it possible in turn to arrange this or that closer to the place where the generated current is needed, for example on the pin arms 5 of a resistance welding device 1.

By the parallel switching of the secondary windings 14 of the high amperage transformer 12, the resulting, high secondary current is divided into several partial currents. These partial currents are transmitted to switching elements 24 of the synchronous rectifier 16, as schematically represented. To activate the switching elements 24, an excitation circuit 17 is provided which is marked in the area of the primary winding 13 and the secondary winding 14, both the synchronous rectifier 16 and the excitation circuit 17 with respective sensor system being arranged inside. of the cube, that is inside the transformer 12 of great amperage. The synchronous rectifier 16 and the excitation circuit 17 are configured and

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dimensioned in this case in such a way that these carry out the regulation and control of the current source 10 autarchically, that is to say without external influence. Therefore, the hub preferably has no control line for engagement from outside, but only connections or contacts for the supply and connections or contacts for the primary supply, and connections or contacts for the supply of the energy generated in the secondary side, in particular of the direct current, secondary high.

However, it is possible that a corresponding connection of the excitation circuit 17 is conducted outwardly, in order to be able to specify to the excitation circuit 17 theoretical values. By means of external adjustments, the current source 10 can be optimally adapted to the field of use. However, as is known from the state of the art, systems for modifying or transmitting data, which work wirelessly, preferably inductively, magnetically or via Bluetooth, can be used, so that no connection of any type control.

The control and / or regulation of the current source 10 is carried out by means of an integrated sensor system. By measuring the secondary currents of a secondary winding 14 with the aid of corresponding current transformers 18, the excitation circuit 17 receives the information on when the switching elements 14 of the synchronous rectifier 16 must be switched. Because the transformers Current 18 only measures a fraction, in this case a tenth of the secondary current of the high-amperage transformer 12, can be made smaller, which positively impacts again on the construction size of the current source 10.

For the reduction of step losses and switching losses, the switching elements 24 of the synchronous rectifier 16 are switched as far as possible in the zero crossing of the secondary currents through secondary windings 14 of the large transformer 12 amperage. Since by registering the zero crossing of the secondary current through the current transformers 18 until an activation of the switching elements 24 of the synchronous rectifier 16 certain delays is reached, the excitation circuit 17 is configured in accordance with the invention for switching the switching elements 24 of the synchronous rectifier 16 at a previously set time before reaching the zero crossing of the current in the secondary winding 14. The excitation circuit 17 therefore causes the switching of the switching elements 24 of the synchronous rectifier 16 at a time when the currents measured by the current transformers 18 in the secondary winding 14 of the high amperage transformer 12 do not reach or exceed a certain connection and disconnection threshold. Through these measures it can be achieved that the switching elements 24 of the synchronous rectifier 16 are substantially switched during the zero crossing of the currents through the secondary winding 14 of the high amperage transformer 12, whereby the step losses and switching losses can be minimized (see also figure 16).

For a primary winding 13 and secondary winding 14, in figure 4 the supply circuit 48 for the supply of the synchronous rectifier 16 and the excitation circuit 17 with electric power is also marked. Also this supply circuit 48 is preferably integrated in the current source 10, ie in the hub. Since the supply of the synchronous rectifier 16 and the excitation circuit 17 of the current source 10 with sufficient electrical power must be guaranteed at the desired moment of the supply of the direct current, for example of the welding current, sufficient activation is necessary of the supply circuit 48 (see figure 15), or it is designed in such a way that in the activation of the current source 10 a sufficiently high supply voltage is provided as quickly as possible, and then the necessary power is supplied or the necessary current.

Figure 5 shows the embodiment of the current source 10 according to Figure 3 in enlarged representation. The current source 10 for facilitating a direct current, for example welding current has substantially the shape of a cube or a parallelepiped, the lateral surfaces of the cube or the parallelepiped representing the contacts 20, 21, 22, 23 through of which the direct current generated for the corresponding consumer can be transmitted, for example the arms 5 of clamps or electrodes 7 of a resistance welding device 1. All components of the current source 10, ie the high current transformer 12, the synchronous rectifier 16, the excitation circuit 17, the current transformer 18, the supply circuit 48 etc. they are contained, either integrated in this element in the form of a cube or in the form of a parallelepiped of the current source 10. By means of this compact construction mode, the losses of the current source 10 can be kept particularly reduced and therefore significantly increase its performance, since an optimal shortening of the lines and therefore of the switching times with the integration of the components is achieved. electronics, in particular of the printed circuit boards with the synchronous rectifier 16, the excitation circuit 17 and the supply circuit 48 in the hub. By integrating the synchronous rectifier 16 and the excitation circuit 17, as well as the supply circuits 48 of the current source 10 into the high amperage transformer 12, as well as the parallel switching of several rectifier switching elements 24 synchronous 16, and the lineless connection of the switching elements 24 with the secondary windings 14 of the high amperage transformer 12, lines between the synchronous rectifier 16 and the secondary side 14 of the high amperage transformer 12 are not necessary, whereby Occasional ohmic losses and additional losses are omitted by lines of this type. The power part 19 for the supply of the high amperage transformer 12 is positioned as close as possible to it, to reach as far as possible short connection lines and therefore power losses and line inductances. By means of the

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Integration of all the components forms an autarkic unit that must be joined on the input side only with the power piece 19, and on the output side, in the case of a resistance welding device 1, with the arms 5 of clamp or electrodes 7. The additional lines between the individual circuits of the current source 10 can be omitted or at least significantly reduced in length.

The base of the high amperage transformer 12 of the current source 10 forms a transformer element in the form of an I-support 25 of electrically conductive material, in particular copper or a copper alloy, in any case with a coating, for example silver. In the notches 25a of the support 25 in I, the magnetic cores 15 are arranged on both sides with the secondary windings 14 of the high amperage transformer 12. In this case it is spatially advantageous if the magnetic cores 15 do not have a round cross-section, but an oval or flat one. In the exemplary embodiment shown, in each case 25a of the support 25 in I five magnetic cores 15 are arranged in each case with the respective secondary windings 14 in parallel. The primary winding 13 or the primary windings 13 (dashed lines and interconnected dots in series run through the magnetic cores 15 arranged in the recesses 25a of the support 25 in I and around the central bridge of the support 25 in I. Through from this course of the primary winding 13 through the magnetic cores 15 arranged in particular symmetrically in the two notches 25a of the support 25 in I an optimal magnetic coupling with respect to the secondary windings 14 can be achieved. The connections 26 of the primary winding 13 are driven outwardly through at least one opening 27 in an outer surface 28 of the 25 in I support. Through these connections 26 the primary winding 13 of the high amperage transformer 12 can be joined with the corresponding power part 19. The outer surface 28 of the support 25 in I forms the first two contacts 20, 21 of the source 10 of the entity, for example, they are joined with one of the electrodes 7 of the resistance welding device 1.

Above the notches 25a of the support 25 in I are contact plates 29 whose outer surfaces form the two additional contacts 22, 23 of the current source 10 and are insulated against the support 25 in I. The contact plates 29 are Likewise formed of electrically conductive material, for example copper or an alloy of lock, in any case with a coating, for example of silver. Copper or copper alloys have optimal electrical properties and show good thermal conductivity so that the thermal losses that appear can be expelled more quickly. The silver coating prevents oxidation of copper or copper alloy. Instead of copper or copper alloys, aluminum or aluminum alloys are also considered, which have a weight advantage over copper, although the corrosion resistance is not so high. Instead of a silver coating, a tin and other materials coating, or their joints or layers, is also possible. Between the contact plates 29 and the corresponding connections of the secondary windings 14 of the high amperage transformer 12 are the printed circuit boards 35 of the synchronous rectifier 16 and the excitation circuit 17. These printed circuit boards 35 or printed circuit boards are mounted or welded directly on the contact plates 29 and are then fixed isolated on the support 25 in I. By this construction mode, the secondary connections of the transformer 12 of large amperage are joined or they are directly contacted with the switching elements 24 of the synchronous rectifier 16 without lines having to be laid. The outputs of the synchronous rectifier 16 are preferably also directly connected to the contact plates 29, so no line is needed. The contact plates 29 are joined with the support 25 in I, preferably screwed (not shown). On the outer surfaces 28 of the support 25 in I, as well as the outer surfaces of the contact plates 29, connection devices 30 can be arranged, for example perforations with corresponding threads to accommodate screws. By means of these connecting devices 30, for example, the lines can be fixed to the clamp arms 5 of a resistance welding device 1, or other devices to be supplied with direct current, or a clamp arm 5 can be fixed directly on the support 25 in I or on contact plates 29.

On the upper side and the lower side of the cube-shaped current source 10, or in the form of a parallelepiped, cover plates 31 may be arranged and joined with the support 25 in I and the contact plates 29, by example be screwed (see figure 6). Preferably, the cover plates 31 are also formed of electrically conductive material, and screwed with the contact plates 29, whereby a stable unit of the high amperage transformer 12 as well as through the cover plates 31 is also produced an electrical connection between the contact plates 29. In this way, it is achieved that a load compensation can take place through the cover plate 31 and therefore no asymmetric load of the high amperage transformer 12 can be reached. Therefore, a separate power line can be suppressed that would electrically link the two contact plates 29 together to produce voltage or potential compensation and avoid asymmetries. Through the cover plates 31, the electrical connection of the two contact plates 29 of the symmetrical arrangement of the high amperage transformer 12 or of the current source 10 to facilitate welding current is therefore produced. In this case, of course a corresponding insulation must be guaranteed with respect to the support 25 in I. The cover plates 31, as well as the support 25 in I and the contact plates 29, are preferably formed of copper or a copper alloy, preferably with a silver coating.

On an outer surface 28 of the support 25 in I, in particular the first contact 20, two inlets 32 are arranged for the admission of a cooling fluid and an outlet 33 for the deviation of the cooling fluid, to enable cooling of the components from the current source 10. The section

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of the outlet 33 to deflect the cooling fluid presents the sum of the cross sections of all the inputs 32 for the admission of the cooling fluid. For optimum flow of the cooling fluid, the cooling channels 39 are arranged correspondingly (see Figures 9 and 11). As a cooling fluid, water or another liquid can be used, but also a gaseous refrigerant.

As can be seen from the exploded view of the current source 10 according to FIG. 6, the current transformers 18 for measuring the secondary currents of the high amperage transformer 12 are placed directly on the secondary windings 14 fully arranged above, that is, in the first secondary winding 14 or higher, a current transformer 18 is arranged on both sides of the support 25 in I, so that due to the induced current, the current can be determined at through this secondary winding 14. To avoid an influence of the currents measured by the current transformer 18 by foreign magnetic fields, a casing 34 of magnetically conductive material, for example ferrlta is preferably arranged for shielding above the transformers 18 of stream.

The current transformers 18 are arranged on both sides of the support 25 in I on the first and second secondary winding 14 in each case. Due to the flow of current through the primary windings 13 the current flows on one side of the support 25 in I, whereby the upper secondary winding 14 thus configures the first secondary winding 14, while on the side facing the current now it enters the upper secondary winding 14 and thus configures the second secondary winding. The use of a complete bridge requires that the current flow is always recorded from the first and second secondary windings 14 independently of one another, so that, depending on the dependence of the current, the corresponding switching elements 24 of the synchronous transformer 16. It is therefore possible that the switching elements 24 of the two sides of the support 25 in I are almost synchronously excited by an excitation signal caused by the current transformer 18.

Between the contact plates 29 and the support 25 in I are arranged the printed circuit boards 35 of the synchronous rectifier 16 and the excitation circuit 17. The printed circuit boards 35 simultaneously form the necessary insulation between the I-holder and the contact plates 29. The corresponding switching elements 24 of the synchronous rectifier 16 are directly connected with the secondary windings 14 of the high amperage transformer 12. By means of corresponding convexities 36, in particular bevel-shaped convexities, on the inner surface of the corresponding contact plate 29 and openings 37 on the printed circuit board 35 below the switching elements 24, a direct splicing of the switching elements 24 with contact plates 29. The switching elements 24 are preferably formed by field effect transistors whose anodes are formed through their housings. The housings of the field effect transistors are joined directly or without lines with the at least one secondary winding 14 of the high amperage transformer 12, so that lines between these units are not necessary. For example, silicon or gallium nitride field effect transistors are used. The current transformers 18 are connected directly with the printed circuit board 35 of the synchronous rectifier 16 arranged to the side and the excitation circuit 17 and by a suitable line 38 with the printed circuit board 35 facing the synchronous rectifier 16 and circuit 17 of excitement

The assembly of the current source 10 according to Figures 5 and 6 is preferably carried out with an indirect welding process using two different indirect welding temperatures. First, the secondary windings 14 are joined with the notches 25a of the support 25 in I using an indirect welding material, in particular a soldering tin that melts at a first higher melting temperature Ts-i, for example a 260 ° C Also the contact plates 29 are spliced with the printed circuit boards 35, using an indirect welding material that melts at the first highest melting temperature TSi, for example at 260 ° C. Then, on the printed circuit board 35, using an indirect welding material, which melts at the first melting temperature Tsi, for example at 260 ° C the components of the synchronous rectifier 16 and the circuit 17 of excitement. By means of the capillary effect of the printed circuit board 35 on the contact plate 29 there is no danger of a separation of the printed circuit board 35 from the contact plate 29. After these working stages, the contacts on the outer side of the secondary windings 14, and the contacts on the printed circuit boards 35 with indirect welding material are filtered with a second melting temperature Ts2 lower with respect to the first temperature melting Tsi, for example at 180 ° C, the contact plates 29 are joined with the printed circuit boards 35 with the support 25 in I, preferably screwed, and then heated by the second melting temperature Ts2 of the welding material indirectly, for example at 180 ° C, so that the secondary windings 14 are connected to the switching elements 24 of the synchronous rectifiers 16. By using an indirect welding material with this second melting temperature Ts2 plus low can be guaranteed that the indirect welding joints manufactured with the indirect welding material with melting temperature Tsi m s high not melt, or by crystallization processes are not high impedance. Finally, the primary winding 13 is threaded through the magnetic cores 15 and then the current transformers 18 are mounted and spliced, and the line 38 is laid. By fixing the cover plates 31 the current source 10 is concluded. In order to reduce tensile and flexural forces on the components of the current source 10, all the cavities can be sneaked before mounting the cover plates 31. Through the openings provided for this purpose (not shown), for example in the cover plates 31, a

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casting also after assembly of the cover plates 31.

Figure 7 shows the current source 10 according to Figures 5 and 6 with indicated course of the cooling channels 39 (drawn with dashed lines). Correspondingly, the cooling channels 39 of the two symmetrically arranged inlets 32 first run towards the contact plates 29, where the most intense heat sources (the switching elements 24 of the synchronous rectifier 16 and the components of the excitation circuit 17 ) and the most sensitive components are cooled with cold cooling fluid. Then, the cooling canes 39 run towards the outer elements of the support 25 in I and towards the central bridge of the support 25 in I, where the windings of the high amperage transformer 12 are cooled, joining the two cooling channels 39 that enter laterally at the central bridge to form a single cooling channel 39. Then, the cooling channels 39 lead to the common outlet 33 for the cooling fluid. The cooling channels in the contact plates 29 and in the support 25 in I are preferably manufactured by corresponding perforations 40 which terminate in the corresponding places by means of termination elements 41. Corresponding sealing elements 42 are arranged between the support 25 in I and the contact plates 29 for sealing the cooling channels 39, for example, o-rings (see Figure 8).

In Fig. 8, the support 25 in I of the high amperage transformer 12 is shown isolated from the other components of the high amperage transformer 12, or from the current source 10. The above-mentioned sealing elements 42 are arranged at the mouths of the cooling channels 39, for example in the form of o-rings. The notches 25a in the support 25 in I are configured exactly for the housing of the magnetic core 15, whereby a very compact construction is achieved. At the same time, the central bridge of the support 25 in I forms the contact surface for the central branch of the secondary windings 14 of the high amperage transformer 12. The central leads of the secondary windings 14 are joined without lines to the central bridge of the support at I 25, whereby the corresponding lines can again be deleted. By means of direct connection of the secondary windings 14 on the support 25 in I, an essential increase in the connecting surface is also achieved, and therefore, loss of passage and power losses can be avoided again.

The support 25 in I forms the base of the high amperage transformer 12 around which the secondary windings 14 are arranged, such that no connecting line is necessary. The outer surfaces of the support 25 in I represent the first two contacts 20, 21 of the current source 10, which directly, that is to say without lines, join with the clamp arms 5 of the resistance welding device 1. A space-saving arrangement is achieved because the magnetic cores 15 are not made round but oval, or flat. Preferably, closed magnetic cores are used. Through this configuration, the serial / parallel switching of the primary windings 13 and the secondary windings 14 can be performed, through which the necessary transmission ratio of the high amperage transformer 12 for the high direct current to be provided is reached. with reduced numbers of turns of the primary windings 13 and secondary windings 14. Such a construction is especially worthwhile if at least three secondary windings 14 are arranged in parallel on each side of the support 25 in I.

Figure 9 shows the image sectioned through the support 25 in I of Figure 8 along the line IX-IX. From this the course of the cooling channels 39 for the common outlet 33 for the cooling fluid can be clearly seen.

Figure 10 shows a contact plate 29 of the high amperage transformer 12, or of the current source 10 as well as the printed circuit board 35 for the synchronous rectifier 16 and the excitation circuit 17 in enlarged representation. As already mentioned above, the switching elements 24 of the synchronous rectifier 16 are connected on one of the sides directly with the corresponding secondary windings 14 of the high amperage transformer 12, and on the other side it is directly connected with the plate 29 of Contact. For this purpose, convexities 36 are arranged on the inner surface of the contact plate 29, in particular bevel-shaped convexes protruding in corresponding openings 37 on the printed circuit board 35 and there they are spliced, directly or without lines, the cathodes of the switching elements 24 arranged above the openings 37. By means of the convexities 36, connection lines between the switching elements 24 of the synchronous rectifier 16 and the contact plates 29 can be waived, whereby on the one hand they can the ohmic losses are reduced, and on the other hand the thermal transition between the switching elements 24 and the contact plates 29 can be improved. Finally, the manufacturing cost is also reduced, since no link line has to be laid or connected, but the switching elements 24 join directly with the convexities 36, preferably they are welded with tin. Also with this, a simple positioning of the Printed circuit board 35 can be made possible and therefore manufacturing can be substantially simplified.

By means of the arrangement of the excitation circuit 17 and the synchronous rectifier 16 on the printed circuit board 35 which is arranged on the inner side of the contact plate 29, the direct connection can be achieved or without lines of the connections of the secondary windings 14 with the switching elements 24 of the synchronous rectifier 16, and also a direct connection or without lines of the outputs of the synchronous rectifier 16 with the contact plate 29. Preferably, the high amperage transformer 12, or the current source 10

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it is constructed symmetrically to facilitate direct current, with both sides of the secondary windings 14 arranged symmetrically arranged in each case a printed circuit board 35 with a part of the synchronous rectifier 16 and the excitation circuit 17 below a plate 29 of Contact in each case.

In the synchronous rectifier 16 according to Fig. 10, ten switching elements 24 in a row are arranged in each case. To ensure that all switching elements 24 switched in parallel are substantially excited at the same time and that the runtime losses have only a small impact, a symmetrical excitation of the switching elements 25 is performed on both sides, i.e. by controllers of gate arranged on both sides are preferably excited in each case five excitation elements 24 from right to left. Other excitation variants can also be arranged, such as a gate controller that additionally runs centrally, whereby the line lengths and their inductances are divided into three parts. A parallel excitation of this type of the gates of the switching elements 24 of the synchronous rectifier 16 ensures short excitation paths, and therefore approximately synchronous switching times of the switching elements 24, since they do not appear, or barely appear loss of runtime In the assembly of the printed circuit board 35, on the contact plate 29, the convexities 36 of the contact plate 29 protrude through the openings 37 in the printed circuit board 35, so that at the same time the side The back of the printed circuit board 35 can be joined or welded with tin with the contact plate 29, and additionally, switching elements 24 arranged on the opposite side also with the contact plate 29 can be attached or welded. Therefore the usual high wiring expense can be suppressed. Also with this, a simple positioning of the printed circuit board 35 on the contact plate 29 is possible, and it can no longer slip during tin welding. If the synchronous rectifier 16, the excitation circuit 17 and the supply circuit 18 are arranged on the printed circuit board 35, an autarkic construction can be achieved in the integration of the printed circuit board 35 into the high amperage transformer 12. It is additionally advantageous if the excitation circuit 17 is arranged on both sides of the switching elements 24 arranged in parallel and in series, since this shortens the line paths to the individual switching elements 24. Therefore, it can be ensured that all switching elements connected in parallel are connected within a very short period of time. By means of the arrangement of the excitation circuit 17 on both sides, a reduction of the line length is achieved by half and thereby accompanied by a reduction of the Line Inductances, and therefore an essential shortening of the switching times 24. On one side of the Printed circuit board 35, a surface that can be indirectly welded to be welded with tin with the contact plate 29 is preferably provided on the entire surface, whereby a secure connection with the contact plate 29 can be achieved. Therefore, the pass-through resistors can also be reduced substantially, since a link across the entire surface of the printed circuit board 35 has a lower pass-through resistance. Instead of the preferred direct connection by indirect welding, short connection cables, the so-called interconnection cables, can also be provided.

The supply circuit 48 is preferably configured to form duly high switching currents, for example between 800 A and 1500 A, in particular 1000 A and for the supply of the components with corresponding supply voltage. Due to the very high switching current a very short switching time can be guaranteed, in particular in the range of ns. With this, it can be ensured that the switching elements 24 always switch to zero crossing, or directly shortly before the zero crossing, with a reduced output current, so that barely any switching losses appear, or none appear. If a data communication circuit is provided for wireless data transmission, preferably inductively, magnetically or via Bluetooth, data can be transmitted wirelessly to and from the printed circuit board 35 (not shown). With this, an adaptation of the switching moments can be made to the different fields of use of the high amperage transformer 12. Likewise, from a memory provided on the printed circuit board 35 (not shown), data can be read for further processing, or controls, or for quality supervision.

In order to create a protection of the switching elements 24 of the synchronous rectifier 16 against overvoltages it is advantageous to switch on the switching elements 24 when they are not needed. In the case of application in a resistance welding device 1, the active synchronous rectifier 16 is therefore activated in the welding pauses to prevent destruction of the switching elements 24. It is monitored whether a primary current or secondary current flows through the high amperage transformer 12, and in the case of no current flow while the electrode holder clamp 4 is positioned correspondingly for a new welding point, circuit 17 excitation activates all switching elements 24 by corresponding excitation of the gate. After positioning of the electrode holder clamp 4, the current source 10 is activated, that is, a manual or automatic welding operation is initiated, then an alternating voltage is applied to the primary winding 13 of the 12 amp transformer 12, which in turn it is detected by the activation circuit 17 due to a current flow, and therefore the protection mode of the switching elements 24 is deactivated. Naturally, the activation and deactivation of the switching elements 24 of the synchronous rectifier 16 can also be carried out by means of control signals that are sent by radio or inductively or magnetically to the excitation circuit 17. In the connected switching elements 24 the possible overvoltages cannot cause any damage. Some minimum protection of the

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switching elements 24 with the aid of zener diodes.

Figure 11 shows an image sectioned through the contact plate 29 according to Figure 10 along the cutting line XI-XI. Hence the course of the cooling channels 39 can be seen remarkably. The openings conditioned by the manufacturing in the perforations 40 for the formation of the cooling channels 39 are sealed by corresponding termination elements 41. The termination elements 41 may be made by corresponding screws that are screwed into corresponding threads in the perforations 40.

Figure 12 shows a magnetic core 15 with two secondary windings 14 of the high amperage transformer 12 arranged above together with the current transformer 18 arranged above, which is shown in an exploded representation. The current transformer 18 is protected with the shield housing 34 and a shield 43 against foreign magnetic fields, so that the secondary current can be measured as accurately as possible by the secondary winding 14 and can be fed to the excitation circuit 17 for control of the excitation elements 24 of the synchronous rectifier 16. For the shielding of magnetic fields ferrites are especially suitable as materials. The current transformer 18 is positioned, or fixed, in this case by a partial area of one of the two secondary windings 14 arranged. As is known from the state of the art, the current transformer 18 is formed from a magnetic core with coil disposed thereon, the coil connections joining the excitation circuit 17. Additionally, the shield 43 and a core plate for the current transformer 18 are arranged between the magnetic core 15 and the secondary winding 14, the current transformer core 18 being placed on this core plate.

In the case of this construction of the high amperage transformer 12, two secondary windings 14 are constructed in this way on both sides of the support 25 in I, so that the excitation circuit 17 measures the current flow through one of the two secondary windings 14 post-cloned and switched on both sides in parallel. If the excitation circuit 17 is connected to these current transformers 18, an exact control or regulation is possible, since through the current transformers 18 the states can be registered in the high amperage transformer 12.

Due to the parallel circuit described above of the secondary windings 14, the same current flows in each secondary winding 14. Therefore, the current of only one secondary winding 14 must be taken as a parameter to be able to deduce from all the current flow. In the case of a parallel circuit of ten secondary windings 14, only one tenth of all current flow is measured by the current transformers 18, so that they can be substantially smaller. Therefore, a reduction in the construction size of the high amperage transformer 12, or of the current source 10, is achieved. It is advantageous if the current transformers 18 are arranged substantially 90 ° oriented towards the direction of the direct current, in particular the welding current, therefore interference through the magnetic field caused by the direct current and therefore errors can be reduced in the measurement. Therefore, a very precise measurement can be made.

As can be extracted from the exploded view according to FIG. 13, the secondary windings 14 of the high amperage transformer 12 are preferably formed by two plates 44, 45 isolated from each other through an insulating layer 46, for example a paper layer, with a substantially S-shaped acronic course around the cross section of a magnetic core 15, and through the magnetic core 15 that are arranged in one another. Two secondary windings 14, or the parts of the secondary winding 14 with central branch, are thus arranged on a magnetic core 15. The external surfaces 47 of the plates 44, 45 of the secondary windings 14 simultaneously form the contact surfaces for the connection with the switching elements 24 of the synchronous rectifier 16 and the support 25 in I, which acts as the central point of the rectification. Therefore, no lines are necessary for the connection of the secondary windings 14 of the high amperage transformer 12 with the switching elements 24 of the synchronous rectifier 16. The secondary windings 14, in particular the plates 44, 45 that configure the secondary windings 14 are they connect directly or without lines with the switching elements 24 of the synchronous rectifier 16 and with the central bridge of the support 25 in I, or the central point of the rectification. This achieves a compact construction that saves a lot of space with little weight and few losses. At the same time, for the connection of the secondary winding 14 with the central bridge of the support 25 in I and the switching elements 24 of the synchronous rectifier 16 relatively large surfaces 47 are provided for a splice to ensure with the lowest possible losses the high flow of stream. By means of this arrangement, a central point rectifier is made on the secondary side on the secondary side, the support 25 in I forming with one of the joined ends of the windings 14 secondary to the central point.

The magnetic core 15 can be formed of ferrites, amorphous materials or nanocrystalline materials. The better the materials used in terms of magnetic properties, the lower the magnetic core 15 can be realized. However, with this the price for the magnetic core 15 naturally increases. In this configuration of the plates 44, 45 it is essential that these they fold or bend, so that at least once they are guided through the magnetic core 15. The two plates 44, 45 arranged on a magnetic core 15 or the secondary windings 14 are configured asynchronous and isolated from each other .

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Figure 14 shows a block diagram of a supply circuit 48, in particular of a supply network for the supply of the synchronous rectifier 16 and the excitation circuit 17 with electric power. The supply circuit 48 joins the secondary side or the connections of the secondary winding 14 of the high amperage transformer 12, and contains a rectifier 49 of maximum values, a voltage booster 50, a length regulator 51 and a divider 52 tensile. The voltage booster 50 or boost converter ensures that the supply of the components of the voltage source 10 is available as quickly as possible. At the same time, the internal supply voltage of the active synchronous rectifier 16 is generated as quickly as possible. By using the voltage booster 50, it is guaranteed in the initial phase of the activation that, on the one hand, the necessary amplitude of the supply voltage is first generated as early as possible to ensure safe operation of the rectifier Synchronous 16 integrated in the high amperage transformer 12 at a time as early as possible.

Figure 15 shows the time course of the supply voltage V of the supply circuit 48 according to figure 14. The ramp of the voltage rise AV / At is selected sufficiently steep to produce the necessary VCC voltage with a time delay maximum Td in synchronous rectifier 16 and excitation circuit 17. For example, the time delay Td should be <200 ps. By means of the corresponding design of the circuits of the rectifier 49 of maximum values and of the voltage booster 50 and the duly low capacities, a sufficient rate of rise of the voltage can be achieved. Therefore, the minimum height of the supply voltage can be said in the first place with a steep rise, and only then the correct supply is established.

Figure 16 shows temporary courses of the secondary current ls of the high amperage transformer 12 and of the control signals Gi and G2 for the switching elements 24 of the synchronous rectifier 16 to illustrate the lossless excitation. By measuring the secondary currents l of a secondary winding 14 with the aid of corresponding current transformers 18, the excitation circuit 17 obtains the information of when the switching elements 24 of the synchronous rectifier 16 must be switched. To reduce the loss of passage and switching losses, the switching elements 24 of the synchronous rectifier 16 are switched as far as possible at zero crossing of the secondary currents through the secondary windings 14 of the high amperage transformer 12. Since the registration of zero crossing of the secondary current ls through the current transformers 18 until the activation of the switching elements 24 of the synchronous rectifier 16 leads to certain delays tpre, the excitation circuit 17 according to the The invention is configured to drive the switching elements 24 of the synchronous rectifier 16 at a previously set time before reaching the zero crossing of the current in the secondary winding 14. The excitation circuit 17 therefore causes the switching of the elements 14 of switching of the synchronous rectifier 16 at a time when the currents ls measured through the current transformers 18 in the secondary winding 14 of the high amperage transformer 12 do not reach, or exceed, a threshold Ise of connection and threshold Isa of disconnection determined. By this measure it can be achieved that the switching elements 24 of the synchronous rectifier 16 are substantially switched during the zero crossing of the currents ls through the secondary winding 14 of the high amperage transformer 12, whereby the step losses and switching losses of the switching elements 24 of the synchronous rectifier 16 can be minimized. The moment of connection and disconnection of the switching elements 24 of the synchronous rectifier 16 is therefore determined not with the zero crossing of the secondary current, but upon reaching the threshold Ise of connection and threshold Isa defined defined. The threshold Ise of connection and threshold Isa of disconnection is defined according to the switching delays to be expected. In any case, the threshold Ise of connection and threshold Isa of disconnection can be configured in an adjustable way to be able to reduce the losses even more. In the case of a transformer 12 of high amperage of 20 kA, for example the switching time of 100 ns can be established before the zero crossing, so that the switching elements 24 of the synchronous rectifier 16 must be switched within this duration.

A conventional state-of-the-art large amperage transformer for a resistance welding device to facilitate a welding current of for example 20 kA exhibits losses of approximately 40 to 50 kW. In total, to facilitate a welding current of 20 kA according to the state of the art, a connection power of up to 150 kW is required, with all losses amounting to 135 I / V, resulting in a yield of approximately 10 %. On the contrary, a transformer 12 of high amperage of the concrete type shows only approximately 5 to 6 kW of losses. Line losses can usually drop from 30 kW to 20 kW. Therefore, in the case of a resistance welding device 1 according to the invention, for the generation of a welding current of 20 kA, the connection power can be reduced to 75 kW, since all losses only amount to approximately 60 Ió / V. The resulting yield is therefore approximately 20% approximately twice as high as in the prior art. This comparison shows very clearly the potential savings possible, particularly in manufacturing trains in the automotive industry with a plurality of resistance welding devices.

Fundamentally, the described current source 10, or the high amperage transformer 12, is configured in the form of a cube or parallelepiped, two lateral surfaces being formed through a support 25 in I, lateral surfaces on which they are arranged electrically insulating contact plates 29 to form the third and fourth lateral surface. On the front side, with respect to the four lateral surfaces, in each case a cover plate 31 is provided which is electrically insulated with respect to the support 25 in I for

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the formation of the fifth and sixth lateral surface of the cube or of the parallelepiped. Within the hub, in particular of the lateral surfaces, the synchronous rectifier 16 and the excitation circuit 17 are arranged on at least one printed circuit board 35 or printed circuit board. The hub therefore has only connections 26 for the primary windings 13 of the high amperage transformer 12 and the lateral surfaces as contact surfaces for the decrease of the direct current, or of the continuous voltage. Additionally, cooling connections are provided, in particular inlets 32 and outlet 33 for a cooling fluid. The control lines for the synchronous rectifier 16 integrated in the hub and the excitation circuit 17 are preferably not provided, since this system operates autonomously and therefore connections with the power part 19 or with a control device are not necessary. of the installation. In the case of such a construction, no type of control line is preferably required, but the current source 10 is only still connected on the primary side with a power piece 19, so on the secondary side, the correspondingly sized direct current of for example 15 kA to 40 kA is available. The user therefore does not need to make any adjustments, but only to connect the current source 10. The unification of the really independent autonomous components to give rise to a common unit of this type causes that the construction size, and therefore the weight of the current source 10, can be substantially reduced. At the same time, the unit can be used as a support element directly in an application, in particular an electrode holder 4. The ease of use is also substantially increased.

In the case of the construction according to the invention it is also essential that the switching elements 24 join without lines with the corresponding components, that is to say the cathodes that conduct the welding current of the switching elements 24 formed by transistors of field effect are connected either soldered with tin directly to the convexities 36 of the contact plate 29, being connected or welded with tin gate connections of the switching elements 24 directly on the printed circuit board 35 and circuit 17 of excitation built on it (gate controller). Therefore the inductances of lines can be reduced by a complete saving of the lines, so that high switching speeds and very low step losses can be achieved.

In the case of the embodiment shown and described, the high-amperage transformer 12 was sized for a current of 20 kA in the case of an output voltage between 5 V and 10 V. In this case, the support 25 in I has a construction height of 15 cm, so that on both sides five secondary windings 14 with the magnetic cores 15 can be arranged in each case. To reach a corresponding transmission ratio of 100, in the embodiment shown, ten are necessary primary windings 13.

If it is now desired to size the high amperage transformer 12 for a higher current of for example 30 kA, then the number of secondary windings 14 used can be increased in a simple manner. For example, on both sides, in the notches 25a of the support 25 in I, seven secondary windings 14 can be arranged in each case, the support 25 in I increasing correspondingly in its height, for example by only 5 cm taller, or a correspondingly larger base body. Therefore the support 25 in I of the transformer 12 of great amperage is added to both sides only in two secondary windings 14 to be able to facilitate a higher current. By increasing the contact cooling surfaces are also increased. Additionally, correspondingly, more parallel switching elements 24 are arranged. The secondary winding 13 can be reduced to a smaller number of turns, for example seven turns, so that a transmission of for example 98 is achieved. Higher primary loop losses are compensated by the higher primary current due to the possible increase of the cross section and the reduction of the line length.

An increase in the secondary welding current from 20 kA to 30 kA therefore results in only a prolongation of the hub, or of the large amperage transformer 12 of for example 5 cm.

Since the high amperage transformer 12 preferably operates autonomously, and does not have any control line, for possible error messages, outward communication with external components, in particular a control device, should be possible. For this, the secondary circuit consisting of the secondary windings 14 and the synchronous rectifier 16 and the excitation circuit 17 can be used. In this case, in certain states, in particular in the no-load operation of the high-amperage transformer 12, it can be consciously short-circuited with the aid of the synchronous rectifier 16, so that by an external supervision unit, or a device of control detects a flow of running current without load on the primary lines and therefore a communication or an error message due to the current can take place.

For example, by integrating a temperature sensor in the high amperage transformer 12, in particular in the synchronous rectifier 16, the temperature can be detected and evaluated. If the temperature rises for example above a defined threshold value, then by the excitation circuit 17, the synchronous rectifier 16 is short-circuited in the run without load, that is to say in the welding pauses in a defined manner. Since the external control device knows the state of running without load during which no welding is performed, it is detected or recognized through the high current flow in the primary ducts of the high amperage transformer 12. Now by the external control device it can be checked if

the cooling circuit is activated, or it has an error, or the cooling power is increased, so that better cooling takes place.

Naturally, by means of switching patterns or corresponding pulses, that is, by means of a defined opening and closing of the switching elements 24 of the synchronous rectifier 16 in the no-load operation, different error messages can be communicated outwards. For example, different temperature values, secondary voltages, currents, error messages, etc. can be sent. outward.

However, it is also possible for such a communication to be made during a weld, although such a detection is noticeably more complicated. In this case, for example, corresponding signals can be modulated in the primary current, in particular by means of the primary windings 13.

10

Claims (6)

5 10 fifteen twenty 25 1. Synchronous rectifier (16) for integration into a current source (10) to facilitate a direct current, in particular in a cube-shaped or parallelepiped unit of a high-amperage transformer (12) with elements ( 24) switching, an excitation circuit (17) to drive the switching elements (24) and a supply circuit (48), a printed circuit board (35) being provided with tracks and connecting surfaces for the housing of electronic components, the switching elements (24), the excitation circuit (17) and the supply circuit (48) for the autarkic operation on the printed circuit board (35), characterized in that on the plate (35) are arranged several openings (37) arranged in parallel and in series are arranged for printed circuits to accommodate convexities (36) of a contact plate (29), openings (37) through which they are arranged and connected, or Tin-welded switching elements (24), switching elements (24) that can be spliced with the convexities (36) of the contact plate (29). 2. Synchronous rectifier (16) according to claim 1, characterized in that the excitation circuit (17) is arranged on both sides of the switching elements (24) arranged in parallel and in series on the circuit board (35) printed. 3. Synchronous rectifier (16) according to claim 1 or 2, characterized in that the excitation circuit (17) is connected with at least one sensor integrated in the high amperage transformer (12), in particular a transformer (18) of current. 4. Synchronous rectifier (16) according to one of claims 1 to 3, characterized in that the supply circuit (48) is configured for the formation of duly high switching currents, for example for the formation of switching currents between 800 A and 1500 A, in particular 1000 A, and for the supply of the components with corresponding supply voltage. 5. Synchronous rectifier (16) according to one of claims 1 to 4, characterized in that a data communication circuit is provided for wireless data transmission, in particular inductive, magnetic or Bluetooth. 6. Synchronous rectifier (16) according to one of claims 1 to 5, characterized in that on one side of the printed circuit board (35) there is provided a surface that can be indirectly welded to be welded with tin with the whole surface. contact plate (29).